The present invention relates generally to the curing of grain in an essentially closed environment and more particularly to a process for minimizing the consumption of energy during the process of curing, while at the same time maintaining maximum quality in grain. Typically, this is accomplished in a round steel bin with a perforated floor and fan means to force air through the stored grain, and dehumidification means to improve air dryness when adverse weather prevails; also having an escape means for exhausting air to the outside. Air movement in grain may be upward or downward to optimize daytime/nighttime conditions.
The practice of field-harvesting grain in an uncured condition greatly increases the risk of deterioration and spoilage. On the surface, it would seem that the high moisture content of the grain is the cause of spoilage. For this reason, equipment has been designed to rapidly extract moisture from the grain using heated air, thereby removing the suspected cause of spoilage. Such equipment has proliferated in various combinations and designs, and is now in widespread usage, with the result that many farmers consume three times more energy in drying corn (at the same time destroying its weight and nutrient value) than they do in producing it.
But the premise upon which the design and production of heated-air drying equipment is based, namely, that moisture in field-harvested grain spoils grain, is false. The application of heat in the forcible removal of water from grain not only represents very large expenditures of monies for equipment, but also represents large expenditures for energy; and in terms of waste, losses resulting from damage to grain is even more costly than the waste of energy.
The fact that a grain kernel is a living seed has all but been overlooked. The economic importance of preserving the living integrity of the seed has been overlooked, and therefore no consideration has been given to the biological limitations of the organism, much less any consideration about regulating its physiological processes which, as a matter of fact, are important not only in optimizing value but also in controlling preservation.
"Drying" and "Curing" are distinct processes. As defined in the Agricultural Engineering YEARBOOK 1977, page 439, "CURING: A form of conditioning as opposed to simple drying in which a chemical change occurs, such as in tobacco, sweet potatoes, etc., to prepare the crop for storage or use." "DRYING: The removal of moisture from a product, usually to some predetermined moisture content." Until now the state of the art has had to do with "drying" of grain, i.e., mere moisture removal, using arbitrary levels of heat and air, but with little or no regard to internal, biochemical changes in the seed. The instant art deals with "curing" in which specific requirements of air quantities and air qualities are made for specific beneficial effects on the live seed.
In that spoilage is generally associated with moisture levels in the seed, and that it must be brought to a "safe level" if above a certain fixed, arbitrary percentage, e.g. 13%, an awareness of a need for "drying" prevails. Also an awareness for the need of rapid harvest prevails and, for drying, therefore, to be practical, it must not inhibit harvest. The conclusion is, therefore, that "fast" harvest requires "fast" drying, and that fast drying is possible only with the use of much air and much heat. Such is the rationale which accounts for the wasteful state of the art that prevails today.
Experience has proven that field-harvesting equipment has far greater capacity than so-called "fast" dryers, consequently, "fast" dryers have become the bottleneck to harvest capacity. However, with storage properly fitted with ventilation equipment, it is possible to harvest the complete crop in a matter of days and to commit the grain to storage, which is capable of stabilizing the grain and of controlling the grain environment by removing moisture and heat as released from the seed, thereby safely extending the time of drying without frustrating harvest speed and without harming the grain.
In U.S. Patent application Ser. No. 422,760, now abandoned, "non" heating of the grain is taught, i.e., chilling stored grain to the wet-bulb temperature by using the free BTU of atmospheric air. This is accomplished by controlled ventilation which evaporates moisture from the grain/air. It is accomplished by using controlled levels of heat input and air volumes in relation to grain moisture and grain volume. In trying to convey an understanding of this new technology, the problem arises that people are so conditioned to accept "heating" of air as a pre-condition to successful drying of grain that they relate to the instant art only in light of preconceived understandings which are based on heated-air drying, and in so doing this teaching is hardly comprehensible to them. A general attitude prevails which lacks an appreciation of the value of preserving "seedlife" and "dormancy".
Since "curing" of grain and the teaching of Steffen is based on understanding seed biology and the natural accomodation that exists between the seed and its environment, the instant art is understandable only with knowledge of interacting physical and biological phenomena. Some of these are:
1. Maximum preservation of food-seeds is obtained by bringing seeds to dormancy under controlled environmental conditions from moment-of-harvest. This is applicable to all food-seeds.
2. Removal of heat from grain is more critical than moisture, in that cooling stabilizes seed chemistry; and temperature is a factor not controlled by the seed.
3. Moisture in the seed is an essential seed ingredient regulated by the seed itself.
4. The elimination of water from the seed is a physiological/chemical process, less effected by atmospheric humidity than by atmospheric temperature under certain conditions.
5. Ventilation requirements are as much a function of seed-temperature as of seed-moisture.
6. Grain is in a "cured" state when its temperature and moisture are in equilibrium with mean, atmospheric temperatures and humidities.
7. Optimum moisture in grain cannot be stated without consideration to grain temperatures.
8. Given adequate ventilation, the temperature and humidity fluctuations which occur daily and seasonally, effectively insure "whole bin" drying and an even equilibrium moisture throughout the bin of stored grain.
9. Atmospheric, daily air conditions require no dehumidification of the air so long as the humidity is at the atmospheric average or below, for the given month.
10. The need for supplemental dehumidification of air is best indicated by evaporative cooling (wet-bulb depression) as occurs within the grain.
11. Lowering of seed moisture and lowering of seed temperature each reflect a stabilizing effect on the grain, and that release of moisture from it is at a slower rate with the lowering of either.
12. That a "dormancy index" for preserving maximum grain stability under atmospheric conditions can be identified as an equilibrium condition of temperature and moisture and is specific for each grain type.
Thus, it can be appreciated that the environmental needs to preserve grain can be defined only if the biological needs are understood. And because no one before Steffen has defined the biological needs, indeed, hardly even recognized the existence of such needs, all kinds of procedures and products have been applied to grain with no real logic. And grain has been the loser, as has been everyone. The losses associated with hot air drying are in terms of (1.) greater expenditures of energy, and (2.) destruction of grain value. In contrast, the benefits experienced in "unheat" curing of grain are that energy consumption is only fractional that of heat methods, and grain shrink is less than 1/2 that of heat methods. Further, because the integrity of the cell systems of the living seed is preserved, No. 1 corn results. Thus, the end product of "unheat" curing is grain whose value has not yet been realized, because heretofore management methods have not preserved such a level of quality. Because of insensitive procedures, genetic value in grain is destroyed, e.g., high lysine content, waxy maise, etc. Because management methods fragment and desiccate seed ingredients, dust accummulations have become a new explosive hazard; however, this method accomplishes preservation of kernel integrity, which virtually eliminates the grain dust hazard.
From the teaching of Steffen in U.S. Pat. No. 3,408,747, it is made clear that specific levels of airflow are required to remove the moisture from the grain environment as it is released by the seed to the surrounding air. It must be understood that the moisture within the seed is not what causes it to spoil, but moisture in the grain air. On the contrary, seed moisture is a necessary resource that the embryonic organism uses to achieve maturity and biological stability. Forced removal of seed moisture with heat as presently practiced, does injury to the embryo in many ways and permanently alters its vegetative and enzyme system, thus, denying the full potential for recovery of food value from grain.
Because of the gross misuse of air and heat in forcibly removing moisture from grain, gross waste results. By carefully defining air quantity and air quality as they relate to seed biology, great savings of energy can result, both as to expenditures required in ventilating grain, and as to energy requirements to maintain the correct dryness in air that is blown through the grain. It is an unrealized fact that it costs the producer less money to preserve seed-perfect corn through curing than it does to produce dead grain through drying without going back to ear corn methods.
In conventional heated-air drying of grain, propane and natural-gas are employed in open-flame burners, so that the products of combustion as well as heat are injected directly into the grain. Not the least of these undesirable products is water itself. For example, the combustion of propane produces more than 11/2 times its own weight in water. Thus, with the 1 to 3 million BTU/hr. burners employed, in a 24 hour period of constant heat, from 200 to 600 gallons of water will be generated and injected into the grain air. Hydrocarbons also contaminate the grain. In addition to creating a biologically hostile environment to grain, the production of water contributes to further unnecessary waste of energy in that it must itself be evaporated from the grain air, and its accummulation in interstitial spaces congest the flow of air causing increased pressures and reduction of air flow. To overcome this congestion of air, it is common practice to apply larger horsepower centrifugal fans. These high-pressure fans are far less efficient than low pressure fans, thus, this substitution of fan design itself accounts for greater expenditures of energy. Waste compounds waste. A single 5 HP vaneaxial fan delivers 9,680 cubic feet of air per minute at 2" static pressure; thus, at the same pressure two 5 HP fans would deliver twice the air volume of a single fan, or approximately 19,360 cubic feet. Contrast that with a 20 HP centrifugal fan which delivers only 16,900 Cfm at 2" static pressure.
With low-pressure drying (under 4" S.P.) as occurs in "unheat" curing, vane-axial fans are most efficiently employed. High-heat/high-pressure grain drying inevitably leads to increased expenditures of energy.